Frost, just south of downtown Victorville (which is hidden behind the rocky hills on the other side of the trees along the Mojave River) is a unique place in railroading. It was here, on a plain created by the river, that Santa Fe constructed a “natural crossover” to allow trains to cross from the standard right-hand operation to left-hand operation, without relying upon switches. This sped up traffic as meets, such as UP special P-YRWC-09, could proceed without one train waiting for the other to clear the usual crossovers. The purpose of left-hand running is that Cajon Pass, the summit of which is eighteen miles away, was originally built in 1883 with a 3% grade from just west of Summit (at a location later named Silverwood) to Cajon. Later, in 1924, a new line was built between these two stations with a gentler 2.2% grade, but to take advantage of these grade differentials, trains operated left-handed over Cajon Pass. On October 13, 2019, Union Pacific’s restored “Big Boy,” 4-8-8-4 4014, operated over what is now the BNSF Railway’s Cajon Subdivision under steam.